1. Field of the Invention
The present invention relates to horsepower indication and monitoring systems, and more particularly, to apparatus for continuously, electronically monitoring the horsepower being transmitted through a shaft as well as operating efficiency of the drive engine causing such rotation.
2. Description of the Prior Art
Numerous situations exist where a shaft is rotated by an appropriate drive mechanism to perform useful work. Exemplary of the same are electric power plants, industrial machine drive systems, propeller-driven ships, and the like. In all of these systems, and in fact in any system in which a powered prime mover causes the powered rotation of a driving shaft, it is extremely important to effectively monitor the horsepower being transmitted through the shaft as well as the overall efficiency of the system including the prime mover, the shaft, and the ultimate output assembly.
In connection with propeller-driven ships, it is extremely important that monitoring equipment simply, yet effectively provide accurate and continuous indications of the horsepower being transmitted through the ship's propeller shafts in order to enable the ship's operating personnel to obtain the optimum performance for developing the maximum output with the least consumption of fuel. While this may be a relatively minor task in connection with small pleasure craft, it becomes a substantial undertaking in connection with large commercial ships such as ocean liners, freighters and tankers. In these latter instances, measurements must be undertaken from one or more engines capable of producing many thousand horsepower and transmitting such power through propeller shafts often many city blocks long and weighing many tons. Yet, these measurements must be accurate, reliable and rapid.
The advantages in installing a shaft horsepower monitoring system are many. From the horsepower and the efficiency information data provided by such system, the operator can readily verify the ship's efficiency, potential faults, and system overloads so as to prevent damage to the assembly and to extend periods between costly overhauls. The data so obtained reduces operating costs, fuel consumption, down time and maintenance, thereby increasing both the ship's reliability and its overall efficiency.
It is also well known to those familiar with large scale propeller driven ships, that where such ships have two main propeller shafts, it is manifestly important that both propellers transmit exactly the same amount of power while underway. While RPM is often used as a close estimate of power being transmitted through the shaft, the same is at best an approximation since the actual amount of power being transmitted through the shaft is effected by many variables such as propeller efficiency, blade angle and diameter. Thus, especially with plural shafts, it is important to monitor the actual power being transmitted through the same since unequal power transmission will inherently cause power drive steering action which, thereafter, would have to be corrected by changing the rudder angle. This develops unnecessary power dissipation from rudder drag with corresponding waste of fuel.
It is also particularly desirable to examine the actual horsepower being transmitted through a ship's propeller during the conducting of sea trials for ship's performance. Large ships for both military and commercial applications must undergo rigorous sea trials at which time data pertaining to virtually every phase of ship's operation is compiled and analyzed before required certification is issued. In these instances, apparatus is necessary to effectively monitor, on a continual basis, the horsepower and fuel consumption efficiency of the ship's power plant while at the same time allowing a permanent recording of such obtained data to be made.
While the prior art, as exemplified by my U.S. Pat. No. 3,274,826, is generally cognizant of systems for directly enabling readout of shaft horsepower, such systems have proven to be only partially satisfactory. This is due to the fact that such systems are typically quite complex, include mechanical sub-systems and/or servo feedback loops, are very costly, are slow responding, are comparatively large, require a null-balance system with wearable precision potentiometers and rotating mechanical members, and cannot be manufactured by integrated, electronic circuit techniques. Thus, a versatile, economical and fully effective monitoring system to meet the needs of today's marine engineer as well as others concerned with the transmission of power through rotating shafts has heretofore been unavailable.